Preheat the oven to 375F and line a large rimmed baking sheet with parchment paper.
In a large mixing bowl, combine the Brussels sprouts, squash, pecans and dates and set aside.
In a smaller mixing bowl, or in a small food processor, combine fresh rosemary, salt, pepper, mustard, coconut oil, apple cider vinegar, garlic, cinnamon, nutmeg and chili powder and whisk (or process) until all the ingredients are well incorporated.
Pour that over the reserved vegetables and mix until well combined.
Transfer the veggies into the prepared baking sheet and bake in the oven for about 40-45 minutes, stirring once or twice during cooking.